An agricultural seeding machine such as a row crop planter or grain drill places seeds at a desired depth within a plurality of parallel seed trenches formed in soil. In the case of a row crop planter, a plurality of row crop units are typically ground driven using wheels, shafts, sprockets, transfer cases, chains and the like. Each row crop unit has a frame which is moveably coupled with a tool bar. The frame may carry a main seed hopper, herbicide hopper, insecticide hopper, furrow opener/closer, etc.
One type of opener/closer arrangement uses a depth gauge wheel which is placed ahead of the leading edge of a single disc opener assembly including a seed tube on the trailing side of the disc. The wheel provides depth adjustment, cleans the leading face of the disc, and limits soil lifting and throw adjacent the disc. One or more closing wheels trail the disc to move soil and close the furrow over the material deposited from the seed tube. Such openers limit soil disturbance, but often a portion of the seed boot or runner operates soil just outside the seed trench which increases soil disturbance, power requirements, wear and seed placement inconsistencies. The leading side wheel axis is close to the disc hub so the wheel operates forwardly of the area where the disc exits the soil so soil lift at the exit point can be a problem, particularly when the operating depth of the disc is increased. If the boot lies outside the furrow, tracking problems are also increased.
With a single disc opener arrangement of this type, the closing wheels trail the seed boot a substantial distance. The actual closing of the furrow occurs sometime after the deposited material reaches the bottom of the furrow, and the material has time to bounce from the bottom of the furrow and as a result the material may be placed shallower than desired. At times, the deposited material can actually bounce completely out of the furrow and lie on top of the ground. Seeds which lie on top of the ground will not germinate. An opener arrangement of this type also has increased geometric space requirements since the gauge wheel, disc opener and closing wheels are sequentially arranged relative to the planting direction.
U.S. Pat. No. 6,347,594 (Wendling et al.), which is assigned to the assignee of the present invention, discloses a furrow opener (FIGS. 1 and 5) having a single disc opener which forms a furrow in the soil. A depth gauge wheel is placed along the trailing edge of the single disc opener, and a further closing wheel is placed so as to generally overlie the seed trench.
What is needed in the art is a furrow opener/closer arrangement which effectively closes a trench formed with a double disc opener at higher ground speeds, with less soil compaction and minimum geometric space requirements.